The present invention relates in general to bore cutting or forming machines and, in particular, to a new and useful device for substantially simultaneously cutting a pair of axially parallel bores which overlap each other so that they share a common cross-sectional area. Such overlapping bores are found for example, in screw-type compressor housings.
While devices are known for cutting two bores, such devices are not suited for making bore holes which intersect each other and thus share a common cross-sectional area. Such intersecting bores must be machined with extreme precision since, in screw-type compressors particularly, the rotary piston which are provided with threads engage each other with a minimum play or in a contact free manner.
It is usual in the prior art to machine the two bores in the housing one after the other by means of a single spindle boring machine. If the diameters of the two intersecting bores are not identical, it is known to machine the two bores with tool holders having different sizes. These tool holders are termed boring heads.
A problem of this prior art method is that the edges formed by the intersection of the two bores cause the bore axis of the boring machine to run off center. To date therefore, only specially trained and highly dependable workmen could be entrusted with this difficult task which in any case is very time consuming.